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/* Instantiate a public key crypto key from an X.509 Certificate
*
* Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public Licence
* as published by the Free Software Foundation; either version
* 2 of the Licence, or (at your option) any later version.
*/
#define pr_fmt(fmt) "X.509: "fmt
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/err.h>
#include <linux/mpi.h>
#include <linux/asn1_decoder.h>
#include <keys/asymmetric-subtype.h>
#include <keys/asymmetric-parser.h>
#include <keys/system_keyring.h>
#include <crypto/hash.h>
#include "asymmetric_keys.h"
#include "public_key.h"
#include "x509_parser.h"
static bool use_builtin_keys;
static struct asymmetric_key_id *ca_keyid;
#ifndef MODULE
static struct {
struct asymmetric_key_id id;
unsigned char data[10];
} cakey;
static int __init ca_keys_setup(char *str)
{
if (!str) /* default system keyring */
return 1;
if (strncmp(str, "id:", 3) == 0) {
struct asymmetric_key_id *p = &cakey.id;
size_t hexlen = (strlen(str) - 3) / 2;
int ret;
if (hexlen == 0 || hexlen > sizeof(cakey.data)) {
pr_err("Missing or invalid ca_keys id\n");
return 1;
}
ret = __asymmetric_key_hex_to_key_id(str + 3, p, hexlen);
if (ret < 0)
pr_err("Unparsable ca_keys id hex string\n");
else
ca_keyid = p; /* owner key 'id:xxxxxx' */
} else if (strcmp(str, "builtin") == 0) {
use_builtin_keys = true;
}
return 1;
}
__setup("ca_keys=", ca_keys_setup);
#endif
/**
* x509_request_asymmetric_key - Request a key by X.509 certificate params.
* @keyring: The keys to search.
* @id: The issuer & serialNumber to look for or NULL.
* @skid: The subjectKeyIdentifier to look for or NULL.
* @partial: Use partial match if true, exact if false.
*
* Find a key in the given keyring by identifier. The preferred identifier is
* the issuer + serialNumber and the fallback identifier is the
* subjectKeyIdentifier. If both are given, the lookup is by the former, but
* the latter must also match.
*/
struct key *x509_request_asymmetric_key(struct key *keyring,
const struct asymmetric_key_id *id,
const struct asymmetric_key_id *skid,
bool partial)
{
struct key *key;
key_ref_t ref;
const char *lookup;
char *req, *p;
int len;
if (id) {
lookup = id->data;
len = id->len;
} else {
lookup = skid->data;
len = skid->len;
}
/* Construct an identifier "id:<keyid>". */
p = req = kmalloc(2 + 1 + len * 2 + 1, GFP_KERNEL);
if (!req)
return ERR_PTR(-ENOMEM);
if (partial) {
*p++ = 'i';
*p++ = 'd';
} else {
*p++ = 'e';
*p++ = 'x';
}
*p++ = ':';
p = bin2hex(p, lookup, len);
*p = 0;
pr_debug("Look up: \"%s\"\n", req);
ref = keyring_search(make_key_ref(keyring, 1),
&key_type_asymmetric, req);
if (IS_ERR(ref))
pr_debug("Request for key '%s' err %ld\n", req, PTR_ERR(ref));
kfree(req);
if (IS_ERR(ref)) {
switch (PTR_ERR(ref)) {
/* Hide some search errors */
case -EACCES:
case -ENOTDIR:
case -EAGAIN:
return ERR_PTR(-ENOKEY);
default:
return ERR_CAST(ref);
}
}
key = key_ref_to_ptr(ref);
if (id && skid) {
const struct asymmetric_key_ids *kids = asymmetric_key_ids(key);
if (!kids->id[1]) {
pr_debug("issuer+serial match, but expected SKID missing\n");
goto reject;
}
if (!asymmetric_key_id_same(skid, kids->id[1])) {
pr_debug("issuer+serial match, but SKID does not\n");
goto reject;
}
}
pr_devel("<==%s() = 0 [%x]\n", __func__, key_serial(key));
return key;
reject:
key_put(key);
return ERR_PTR(-EKEYREJECTED);
}
EXPORT_SYMBOL_GPL(x509_request_asymmetric_key);
/*
* Set up the signature parameters in an X.509 certificate. This involves
* digesting the signed data and extracting the signature.
*/
int x509_get_sig_params(struct x509_certificate *cert)
{
struct crypto_shash *tfm;
struct shash_desc *desc;
size_t digest_size, desc_size;
void *digest;
int ret;
pr_devel("==>%s()\n", __func__);
if (cert->unsupported_crypto)
return -ENOPKG;
if (cert->sig.rsa.s)
return 0;
cert->sig.rsa.s = mpi_read_raw_data(cert->raw_sig, cert->raw_sig_size);
if (!cert->sig.rsa.s)
return -ENOMEM;
cert->sig.nr_mpi = 1;
/* Allocate the hashing algorithm we're going to need and find out how
* big the hash operational data will be.
*/
tfm = crypto_alloc_shash(hash_algo_name[cert->sig.pkey_hash_algo], 0, 0);
if (IS_ERR(tfm)) {
if (PTR_ERR(tfm) == -ENOENT) {
cert->unsupported_crypto = true;
return -ENOPKG;
}
return PTR_ERR(tfm);
}
desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);
digest_size = crypto_shash_digestsize(tfm);
/* We allocate the hash operational data storage on the end of the
* digest storage space.
*/
ret = -ENOMEM;
digest = kzalloc(digest_size + desc_size, GFP_KERNEL);
if (!digest)
goto error;
cert->sig.digest = digest;
cert->sig.digest_size = digest_size;
desc = digest + digest_size;
desc->tfm = tfm;
desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
ret = crypto_shash_init(desc);
if (ret < 0)
goto error;
might_sleep();
ret = crypto_shash_finup(desc, cert->tbs, cert->tbs_size, digest);
error:
crypto_free_shash(tfm);
pr_devel("<==%s() = %d\n", __func__, ret);
return ret;
}
EXPORT_SYMBOL_GPL(x509_get_sig_params);
/*
* Check the signature on a certificate using the provided public key
*/
int x509_check_signature(const struct public_key *pub,
struct x509_certificate *cert)
{
int ret;
pr_devel("==>%s()\n", __func__);
ret = x509_get_sig_params(cert);
if (ret < 0)
return ret;
ret = public_key_verify_signature(pub, &cert->sig);
if (ret == -ENOPKG)
cert->unsupported_crypto = true;
pr_debug("Cert Verification: %d\n", ret);
return ret;
}
EXPORT_SYMBOL_GPL(x509_check_signature);
/*
* Check the new certificate against the ones in the trust keyring. If one of
* those is the signing key and validates the new certificate, then mark the
* new certificate as being trusted.
*
* Return 0 if the new certificate was successfully validated, 1 if we couldn't
* find a matching parent certificate in the trusted list and an error if there
* is a matching certificate but the signature check fails.
*/
static int x509_validate_trust(struct x509_certificate *cert,
struct key *trust_keyring)
{
struct key *key;
int ret = 1;
if (!trust_keyring)
return -EOPNOTSUPP;
if (ca_keyid && !asymmetric_key_id_partial(cert->akid_skid, ca_keyid))
return -EPERM;
key = x509_request_asymmetric_key(trust_keyring,
cert->akid_id, cert->akid_skid,
false);
if (!IS_ERR(key)) {
if (!use_builtin_keys
|| test_bit(KEY_FLAG_BUILTIN, &key->flags))
ret = x509_check_signature(key->payload.data, cert);
key_put(key);
}
return ret;
}
/*
* Attempt to parse a data blob for a key as an X509 certificate.
*/<
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